When the client is in full-screen mode, it sits on top of any system UI elements, like the menu bar and dock on macOS. This is expected and desired. But the user might want to be able to reach those system UI elements without leaving full screen, as that is how macOS native full screen behaves. We should consider mimicking the native full-screen experience better by having the same auto-hide behaviour.
This can be achieved on macOS by calling: > [NSApp setPresentationOptions:NSApplicationPresentationAutoHideMenuBar|NSApplicationPresentationAutoHideDock]; But we probably need to stop fiddling with the layering, which means we need to find a different way to do keyboard grabs (bug 4660).